author(s)
MA Patil, PR Palande, SR Kulkarni and ST Aghav

abstract
The present investigations on “Bioefficacy of Heterorhabditis indica (Poinar) against Helicoverpa armigera (Hubner)” was carried out during the year 2018-19 at Research Laboratory, Department of Agricultural Entomology, Post Graduate Institute, Mahatma Phule Krishi Vidyapeeth, Rahuri (M.S.). The bioefficacy of different doses of H. indica was studied against 3^rd, 4^th and 5^th larval instars of H. armigera. Larvae were exposed to 0 (control), 25, 50, 75, 100, 150, 200 infective juveniles (IJs) per ml per petri dish and for various time periods (24 hr, 48 hr and 72 hr). It was observed that among all doses, the dose with 200 IJs/ml brought quicker 100 per cent mortality as compared with other lower doses which brought slower mortality. It was also observed that the third instar showed mortality ranged from 26.67 to 63.33 per cent 24 HAE. 48 and 72 HAE mortality ranged from 43.33 to 90 per cent and 80 to 100 per cent, respectively. In case of 4^thinstar larvae 24 HAE larval mortality ranged from 23.33 to 60.00 per cent, 48 HAE 40.00 to 86.67 per cent and 72 HAE 63.33 to 100 per cent. In case of 5^th instar mortality range recorded was 20.00 to 56.67 per cent for 24 HAE, in case of 48 HAE it was 33.33 to 90.00 per cent and 72 HAE range was from 46.66 to 100 per cent. Thus it was concluded that mortality percentage increase with increase in time of exposure. The LC₅₀values for 3^rd, 4^th and 5^th instar H. armigera larvae when exposed to 72 hr period were 12.09, 21.88 and 32.91 IJs of H. indica per ml of water, respectively, whereas 3^rd, 4^th and 5^th instar larvae exposed for 24 hr period showed LC₅₀values 99.99, 118.92 and 140.07 IJs per ml of water, respectively. The LC50 values were less when H. armigera larvae were exposed for 72 hr as compared to 24 hr exposure period which meant 3^rd instar H. armigera larvae exposed for 72 hr were more susceptible as it required less number of IJs/ml to bring about 50 per cent mortality than 4^th and 5^th instar larval stages.